During the training phase, maintaining Caloric balance (eating enough
Calories to replace those used during
the day's exercise) is the biggest challenge faced by endurance athletes.
Not only will daily Caloric requirements be significantly beyond normal
dietary intake, the time available to eat (including snacks) is reduced by
the time requirements of the training itself. This is particularly true with
swimming and running as snacking while exercising is almost impossible. To
avoid slowly losing ground nutritionally, you will need to closely monitor
your daily Caloric expenditures, make a conscious attempt to snack throughout
the day to replace thoise Calories, take advantage of the post exercise
glycogen replacement window to restock muscle glycogen stores for the next
day's training, and weight yourself daily to be sure you are staying
in "Caloric balance".

How about the triathlon itself? Nutrition during the
pre-event interval (4 days, 4 hours,
4 minutes) is essentially the same as for all other competitive events.
The body can store only so much glycogen in the muscles and liver during
the 4 days before the competition, and the digestive tract can handle only
so much volume in the 4 hour pre event meal. But the triathlete can take
advantage of the 30 to 60 minutes before the event to take a final
carbohydrate "boost". As eating while swimming is impossible
and inadvertently swallowing water the rule, it makes sense to eat enough
complex carbohydrate gel or drink (which will then be slowly emptied into
the small intestine over the duration of the swim - with fluids being
provided from swallowed water) to replace the Calories that will be expended
during the swim (8 to 10 Calories/minute). To minimze GI upset, these
carbohydrate Calories should be taken at least 30 to 60 minutes before
the swim.

The energy requirements of cycling have been covered elsewhere. As with
all cycling events, the key to success is snacking - starting early (during
the transition) and continuing to snack regularly during the ride. In the
triathlon, where you will be finishing the event with a run, snacking is
even more important as any extra Calories taken on board will not only make
up for any Caloric deficit from the swim, but will also be available to help
you during the run when snacking is much more difficult.

When the run begins, the athlete should be Calorie neutral ie the Calories
eaten in the minutes before the swim and during the cycling should equal or
slightly exceed the Calories expended during the swim and the ride. Now
begins the real challenge - to replace as many of the Calories that will be
expended with the run as possible. Running will slow gastric emptying and as
a result, snacking may cause nausea. But the new gels and liquid supplements,
if taken in small amounts, regularly, can help minimize the phenomena
of "hitting the wall" late in the run.

Remember, along with staying hydrated, Calories are the key, carbohydrates
are preferred, and anticipting and replacing your energy needs with regular
snacking before you notice hunger will be the most successful strategy.